Microbiota contributes to an array of benefits for their human hosts; digestion, vitamin production, homeostasis, immunity and the list goes on. The microbiome is first established upon exit from the sterile womb, and the mode of delivery can shape colonisation and dynamics of a newborn’s gut community.
A recent article from BBC highlights gut microbiome differences between vaginally and Caesarean-section (C-section)-delivered Scottish and Dutch infants. According to the article, vaginally delivered infants raised double the amount of antibodies in response to childhood vaccines than those born by C-section.
What do the studies show?
According to the studies, differences in beneficial commensal bacteria mediate the immune response to vaccines, with vaginal delivery enriching for more commensal bacteria in infants. Vaginally delivered infants are first introduced to the microbes in their mothers’ genitals, which include commensal stool organisms and lactic acid-producing lactobacilli. Conversely, C-section newborns are introduced to microbes on the skin or in the hospital or home. These microbes typically include members of the Staphylococcus and Cutibacterium genera, which are generally not commensal gut organisms and may not be as beneficial to the developing gut microbiome and immune system.
The differences in microbial colonizers of vaginally and C-section-delivered newborns and the implications this could hold for immune system development has lead to studies investigating gut microbiome variation and its role in immunity in infants. A common focus of those studies is immune response variation in newborns.
In a study from the University of Edinburgh, Spaarne Hospital and Utrecht University Medical Centre, researchers examined gut microbiome variation in newborns. They collected the first faecal sample of life, called meconium, from 120 newborns. Then they sequenced the 16S rRNA gene in all samples to profile the bacterial composition at the species level. Whole genome shotgun sequencing was also performed on a subset of meconium samples to validate the microbiome findings of the 16S rRNA profiling.
The findings from the study illustrated higher levels of Bifidobacterium and Escherichia coli species associated with anti-pneumococcal antibody response in vaginally delivered newborns. This suggests an important role of these taxa in heightening vaccine responses, and that vaginal delivery may be important to their establishment.
On this point, Professor Debby Bogaert, the chair of paediatric medicine at the University of Edinburgh, highlights the importance of the first interaction between the host immune system and microbes. According to her, the release of short chain fatty acids (SCFAs) by gut bacteria marks the activation time of the newborn immune system. When SCFA production is lacking, there are fewer B-cells to produce antibodies.
Due to the lack of transfer of beneficial commensal microbes following a C-section delivery, the use of some type of seeding mechanism has been proposed. To replace the missing microbiome, studies have attempted to seed caesarean delivered newborns with the vaginal and gut microbes of their mothers. Yet, Prof. Bogaert approaches these attempts with caution, emphasizing that, in practice, safely transplanting microbes to infants may be complicated and even dangerous.
The risks would be confounded when considering the high number of babies born by C-section. To overcome these risks, Prof Bogaert suggests that giving a precise bacterial supplement may do the trick. These are recent findings from a relatively small study, but may be paving the way for a future where microbes could be manipulated to improve the immune systems of C-section-delivered babies.
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